1. Field of the Invention
The present invention relates to liquid mycorrhiza compositions and to methods for colonizing a plant, grass, tree or shrub with one or more mycorrhizas. Specifically, it relates to compositions which improve the ability of the mycorrhizas to colonize plant roots, resulting in greater efficacy of plant treatment formulations which contain the mycorrhizas.
2. Description of Related Art
Mycorrhizas are symbiotic associations between fungi and the roots of plants. In a mycorrhizal association, the fungus may colonize the roots of a host plant either intercellularly, intracellularly or extracellularly. The functional symbiosis provides a suitable and sufficient carbohydrate source for the fungal symbiont. The plant symbiont benefits can be numerous and include improved nutrient and water uptake, additional carbon acquisition, increased sink strength for photosynthate translocation, increased production of phytohormones, improved resistance to pathogens, and heavy metal tolerance. Mycorrhizas are critically important organs for resource uptake by most terrestrial plants. In the absence of an appropriate fungal symbiont, many terrestrial plants suffer from resource limitations and ultimately reduced growth, and fitness.
Mycorrhizas are added to fertilizer products to incorporate beneficial mycorrhizas in the fertilizer blends. Current fertilizer blends contain mycorrhizas in the form of a dry granular product or a wettable powder product. Mycorrhizas have not been added to liquid fertilizers due to stability issues.
Production of mycorrhizas is challenging because they have unique growth requirements. Endomycorrhizas (also called vesicular arbuscular mycorrhizas, VAM, or arbuscular mycorrhizas, AM) are obligate symbionts with plants. The predominant method used to cultivate the endomycorrhizas is with a host plant under controlled conditions.
Bactericides are commonly used to eliminate unwanted bacterial contamination. The preservatives used at low rates are designed to kill vegetative bacteria while leaving spores unharmed. Kathon (methylchloroisothiazolinone and methylisothiazolinone) and Bronopol (2-bromo-2-nitro-1,3-propanediol) are two bactericides used as preservatives. Kathon has a broad antimicrobial spectrum. It is effective against gram-negative and gram-positive bacteria, fungi, and yeasts. Bronopol is effective in killing gram-negative and gram-positive bacteria. Depending on the amount used, the bactericide can kill bacteria or keep them in the spore form.
CN 1420167 discloses liquid inoculants basically connected with ectomycorrhizas.
JP 4141023 discloses a liquid medium comprising a stabilizer (citric acid or its salt form) to protect the spores.
US 2004/0208852 discloses a method of colonizing a plant with mycorrhiza.
WO 2006/060968 discloses a liquid mycorrhizal inoculant.
Schreiner et al. (Biol. Fertil. Soils, 1997, 24:18-26) describe the effects of biocides on arbuscular mycorrhizas.
Al-Garni (World Journal of Agricultural Sciences, 2006, 2(3): 303-310) describes the influence of malathion and mancozeb on mycorrhizal colonization.
West et al. (Journal of Ecology, 1993, 81(2): 345-350) describe the influence of three biocides on the fungal associates of the roots of Vulpia ciliata. 
It is an object of the present invention to provide a liquid mycorrhiza composition comprising mycorrhiza which increases mycorrhizal colonization.